Callum is the quartermaster and surgeon for the crew of The Dragon's Serenity, a light cargo ship sailing under Ronsonian colors even if it isn't officially a ship operated by the Ronsonian government. He forges all of the swords used by his crew.
Callum has a tattoo on the back of his head in the form of the Ronsonian glyph for "Wisdom". It magically provides him with answers and sage advice when he interacts with others. He is usually quite calm and reserved. He is also the (fraternal) twin brother to Gavin, the Dragonmyst; he had been given to the Hal family of Ronso - a family with whom his uncle Arroues was friends - and he grew up with his captain, Rinna Hal.